1. Technical Field
The present invention relates to a photocurable resin composition, an image display device using this photocurable resin composition, and a method for manufacturing the same.
2. Background Art
Photocurable resin compositions are widely used as an adhesive; a pressure-sensitive adhesive; a filler; an optical member such as an optical wave guide, a member for solar batteries; a light emitting diode (LED), a phototransistor, a photodiode, an optical semiconductor element, an image display device, an illumination device, etc.; a dental material; and the like.
For example, there is proposed a method in which in an image display device, an air gap between a transparent protective plate or an information input device (for example, a touch panel, etc.) and a display surface of an image display unit, or an air gap between a transparent protective plate and an information input device, is displaced with a transparent material having a refractive index closer to that of the transparent protective plate, the information input device, and the display surface of the image display unit than that of air, thereby enhancing the transmittance and suppressing a lowering of the luminance or contrast of the image display device. Then, it is proposed to use an adhesive which is cured by ultraviolet rays or visible rays as this transparent material (for example, JP-A-2008-83491). An example of a diagrammatic view of a liquid crystal display device as this image display device is shown in FIG. 1. A liquid crystal display device with a built-in touch panel is configured of a transparent protective plate (glass or plastic base material) 1, a touch panel 2, a polarizing plate 3, and a liquid crystal display cell 4. For the purposes of preventing the breakage of the liquid crystal display device, relaxing the stress and impact, and enhancing the visibility, there may be the case where a pressure-sensitive adhesive layer 5 is provided between the transparent protective plate 1 and the touch panel 2, and a pressure-sensitive adhesive layer 6 is further provided between the touch panel 2 and the polarizing plate 3.
As the photocurable resin composition, those in a liquid form or film form are known.
For example, JP-A-2009-1654 discloses a photocuring type transparent adhesive composition containing a urethane (meth)acrylate (A) having two or more functional groups having an unsaturated double bond, a monomer (B) having one functional group having an unsaturated double bond, a photopolymerization initiator (C), and a polythiol compound (D) having two or more thiol groups.
In addition, JP-A-2011-74308 discloses a transparent pressure-sensitive adhesive sheet composed of a photocurable resin composition containing a copolymer of a monomer component containing an alkyl (meth)acrylate in which the alkyl group has a carbon number of from 4 to 18, and the like.
Now, as a technology for gelling an oil, the addition of an oil gelling agent to the oil is carried out. The oil gelling agent is characterized in that the molecule forms a network in the oil, thereby achieving thickening. It is possible to gel the oil by dispersing a low-molecular weight oil gelling agent in the oil under heating conditions and cooling the dispersion to room temperature.
When the photocurable resin composition is in a liquid form as in JP-A-2009-1654 or the like, at the time of forming in a prescribed place, there is involved such a problem that the photocurable resin composition is liable to leak out from the subject prescribed place.
On the other hand, when the photocurable resin composition is in a sheet form (solid form) as in JP-A-2011-74308, though the problem of leakage is not caused, there is involved such a problem that the photocurable resin composition does not sufficiently deform after the shape of a prescribed place, thereby likely generating an air gap or the like in the subject prescribed place.